DNA Replication

My AP Biology Thoughts Unit 6 Gene Expression and Regulation

Welcome to My AP Biology Thoughts podcast, my name is Morgan and I am your host for episode # 106 called Unit 6 Gene Expression and Regulation: DNA Replication. Today we will be discussing the process by which cells replicate their DNA

Segment 1: Introduction to DNA Replication

• Difference between prokaryotic and Eukaryotic DNA
• P is one circular piece of dna where eukaryotic are multiple linear chromosomes
• DNA replication is semi-conservative
• Double helix is split in two and then each new strand is synthesized so to new double helices are made, each with one old and one new strand
• very complex but very fast
• Extremely accurate (only 1 in a billion bases are messed up)
• Have to prime the DNA for replication
• Primers are short molecules that attach to the dna at the origin of replication
• Mde by the enzyme primase
• Helicase is the enzyme that unwinds the double helix- initiates the replication fork (where two strands split apart)
• Multiple replication forks in eukaryotic dna
• Topoisomerase checks problems in the DNA before replication and maintains the structure
• DNA polymerase is the enzyme that synthesizes the new DNA strand- reads the bases and matches up complementary nucleotides

Segment 2: More About the process of replication

• Replication initiation can occur at both directions from the origin where the primer binds
• DNA polymerase can only add nucleotides in the 5 to 3 prime direction, and read the strand of dna in the 3 to 5 prime direction
• Leading strand is continuous
• Lagging strand is discontinuous, has to read and synthesize in short segments (okazaki fragments)
• Enzyme ligase seals together the fragments
• Energy needed for this process (remember forming bonds between the nucleotides requires energy)

Segment 3: Connection to the Course

• Connection to mitosis
• S phase of mitosis is dna replication
• Necessary for cell division to make the same amount of chromosomes in...